Pressure-sensitive recording materials, which utilize the color reaction between an electron-donating color former (hereinafter, "color former" for short) and a color developer, for example, clay such as acid clay, activated clay, attapulgite, zeolite, bentonite or kaolin, a metal salt of an aromatic carboxylic acid or a phenol-formaldehyde resin, are well known in the art and are described, for example, in U.S. Pat. Nos. 2,505,470, 2,505,489, 2,550,471, 2,548,366, 2,712,507, 2,730,456, 2,730,457 and 3,418,250 and Japanese Patent Publication (unexamined) Nos. 28411/1974 (corresponding to U.S. Pat. No. 3,896,255) and 44009/1975.
However, the pressure-sensitive recording materials in which the above color developers are used are not satisfactory in terms of fastness of the developed images to light and/or solvents and other disadvantages.